The present invention relates to a process for producing L-amino acids by fermentation. L-amino acids are used as drugs, food products and feed additives.
As the direct fermentation methods for producing L-amino acids directly from sugars, there are known methods in which mutants derived from wild type strains of microorganisms belonging to the genus Corynebacterium, Brevibacterium, Escherichia, Serratia or Arthrobacter are employed. For example, the following are known as L-amino acid-producing mutants: auxotrophic mutants which require amino acids, etc. (Japanese Published Examined Patent Application No. 10037/81), mutants which have resistance to amino acid analogues, vitamins, etc. (Japanese Published Unexamined Patent Application No. 134993/81, Japanese Published Unexamined Patent Application No. 44193/87), mutants which have both auxotrophic mutation and resistance mutation to amino acid analogues (Japanese Published Unexamined Patent Application No. 31093/75, Japanese Published Unexamined Patent Application No.134993/81), mutants which have lowered degradability (Japanese Published Unexamined Patent Application No. 273487/88, Japanese Published Examined Patent Application No. 48195/77) and mutants whose aminoacyl t-RNA-synthesizing enzymes have a decreased substrate affinity (Japanese Published Unexamined Patent Application No. 330275/92). Also known are transformants obtained by transformation with recombinant DNAs containing genes related to the biosynthesis of amino acids (Japanese Published Unexamined Patent Application No. 893/83, Japanese Published Unexamined Patent Application No. 12995/85, Japanese Published Unexamined Patent Application No. 30693/85, Japanese Published Unexamined Patent Application No.195695/86, Japanese Published Unexamined Patent Application No. 458/90, Japanese Published Unexamined Patent Application No. 42988/90).
Because of a growing demand for L-amino acids for use as drugs, food products and feed additives in recent years, there is an increasing need for the improvement of processes for producing L-amino acids. An object of the present invention is to provide an industrially efficient process for producing L-amino acids which are useful as drugs, food products and feed additives.